A. Field of the Invention
The present invention relates to the combination of an injection molding device with a microprocessor, and a method to produce capsules of a moldable hydrophilic polymer composition, preferably gelatin. The present invention utilizes gelatin, preferably made from various types of gelatin including acid or alkaline processed ossein, acid processed pigskin, or alkaline processed cattle hide. Said types of various gelatin have a molecular mass range of 10,000 to 2,000,000 Dalton or a molecular mass range of 10,000 to 2,000,000 and 10,000,000 to 20,000,000 Dalton. The method for determination of the molecular mass distribution of the various types of gelatin used in the present invention is performed as described in the following references:
I. Tomka, Chimia. 30, 534-540 (1976) PA1 I. Tomka, et al, Phot. Sci. 23, 97 (1975)
Gelatin having a molecular mass range between 10,000 and 2,000,000 Dalton, was found to give less deformation of capsule parts after ejection from a capsule mold,
When in the following description the term "gelatin" is used, other hydrophilic polymers whose properties were acceptable as capsule materials are also included. Hydrophilic polymers are polymers with molecular masses from approximately 10.sup.3 to 10.sup.7 Dalton carrying molecular groups in their backbone and/or in their side chains and capable of forming and/or participating in hydrogen bridges. Such hydrophilic polymers exhibit in their water adsorption isotherm (in the temperature range between approximately 0.degree. to 200.degree. C.) an inflection point close to the water activity point at 0.5. Hydrophilic polymers are distinguished from the group called hydrocolloids by their molecular dispersity. For the maintenance of the molecular dispersity of said hydrophilic polymers a fraction of water-according to the working range of the present invention-of 5 to 25% by weight of said hydrophilic polymers must be included provided that the temperature of said hydrophilic polymers is in the working range between 50.degree. C. and 190.degree. C. of the present invention.
There are other hydrocolloids, not hydrophilic polymers in the sense of this definition, which contain more or less spherical or fibrous particles whereby those particles are composed of several macromolecules of a hydrophilic polymer within the molecular mass range of 10.sup.3 -10.sup.7 Dalton giving rise to particle sizes between 0.01-10 microns which is the typical range of colloidal particles. It is a primary object of the present invention to utilize hydrophilic polymers in the production of capsules.
B. Reference to Copending Patent Applications
Concurrently with this application, please also refer to patent application U.S. Ser. No. 362,177 filed Mar. 26, 1982 and to patent application U.S. Ser. No. 362,430 filed Mar. 26, 1982, both of which are copending with this application.
C. Description of the Prior Art
Capsule-making machines have been developed to utilize dip-molding technology. Such technology involves the dipping of capsule-shaped pins into a gelatin solution, removing the pins from the solution, drying of the gelatin upon the pins, stripping off the gelatin capsule parts from the pins, adjusting for length, cutting, joining and ejecting the capsules. Prior art capsule-making machines have utilized the combination of mechanical and pneumatic elements to perform these functions at speeds up to about 1,200 size 0 capsules per minute. While the above described apparatus are in general suitable for the intended purposes, it is desirable to produce capsules at considerably higher speed, over 15,000 size 0 capsules per minute, while at the same time precisely controlling the properties of the gelatin in order to produce the capsules hygienically and with minimum dimensional deviations so that the capsules can be filled on high speed equipment.
Shirai et al. in U.S. Pat. No. 4,216,240 describes an injection moldng process to produce an oriented fibrous protein product. The fibrous product as obtained by this process differs fundamentally from the transparent glasslike material of the capsules obtained from the present invention. Furthermore to obtain a flowable mass for the molding process, the protein mixtures used by Shirai et al. have to be denatured and thus lose their capacity to undergo dissolution.
Nakatsuka et al. in U.S. Pat. No. 4,076,846 uses binary mixtures of starch with salts of protein materials to obtain an edible shaped article by an injection molding process. With the present invention shaped articles from protein materials, preferably gelatin and other hydrophilic polymers can be produced without the addition of starch.
Heusdens et al. in U.S. Pat. No. 3,911,159 discloses the formation of filamentous protein structures to obtain edible products of improved tenderness. With the present invention shaped articles are produced without a filamentous protein structure.
The use of an injection molding device for producing capsules of gelatin and other moldable hydrophilic polymers with similar properties is new and has not been suggested in the technical literature. A prerequisite for any material to be moldable by an injection process is its ability to pass a glass transition point at a temperature compatible with the thermal stability of the material and the technical possibilities of an injection molding device.
The present invention provides an improved injection molding method adapted to be automatically controlled by microprocessing techniques and utilizing molding compositions in the form of hydrophilic polymers, such as gelatin, possessing a dissolution point within a temperature range usable for an injection molding process, and which permit the water content to be controlled within a predetermined range to avoid the need for additional steps of either drying or humidifying of the molded product formed by the injection molding device.